Driving device

ABSTRACT

A driving device includes a frame, a screw-nut system comprising a threaded rod and a first nut helicoidally connected to the threaded rod, the threaded rod being connected to the frame by a pivot connection that allows the threaded rod to rotate with respect to the frame about a longitudinal axis of the threaded rod, a first position sensor making it possible to detect a limit position of the first nut along the longitudinal axis, the first position sensor comprising a first part and a second part, the first position sensor being sensitive to a variation in a distance between the first part and the second part of the first position sensor along the axis, the first part being fixed to the first nut and the second part being connected to the threaded rod without passing via the pivot connection and in such a way that rotation of the threaded rod about the longitudinal axis leads to a variation in the distance between the first part and the second part of the first position sensor along the longitudinal axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International patent applicationPCT/EP2017/084615, filed on Dec. 27, 2017, which claims priority toforeign French patent application No. FR 1601869, filed on Dec. 27,2016, the disclosures of which are incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to nut-driving devices comprising ascrew-nut system. In devices of this type, the rotation of a threadedrod causes the translational movement of a nut, connected to thethreaded rod by a helicoidal connection, along the longitudinal axis ofthe rod.

BACKGROUND

This type of device is implemented in particular in detection devicesfor helicopter-borne warfare against submarine threats, in which anantenna for detecting submarine threats is suspended from an aerialplatform such as an aircraft which makes it possible to dip the antenna.The antenna comprises the emitters and receivers per se, and potentiallyelectronic equipment associated with the emitters and receivers. It mayalso comprise environmental sensors. Moreover, on board the aerialplatform, the detection device comprises equipment required forgenerating the acoustic signals and for processing the received acousticdata.

An example of a detection device is shown in FIG. 1 . It comprises awinch 100 designed to be installed in an aerial platform. The airbornewarfare device comprises an antenna 101 suspended at the end of anelectric/hoisting cable 102 of the winch 100, possibly provided with afunnel 103 as is the case in FIG. 1 . The winch 100 is designed todeploy and recover the antenna 101. In FIG. 1 , the winch 100 is securedto a floor 200 of an aerial platform. The electric/hoisting cable 102serves to carry signals and the electrical energy required for theacoustic emission and/or the operation of the receivers. Unwinding thecable 102 using the winch 100 lowers the antenna 101 through the funnel103 (if present) and into the water. Hauling in the cable 102 serves toraise the antenna 101 into the aerial platform within the funnel 103 (ifpresent) as shown in FIG. 1 .

The antenna 101 is in the form of an essentially cylindrical elongatedome. It comprises an elongate body 112 having an outer circumference ofessentially circular cross section in a plane perpendicular to thelongitudinal axis z of the antenna 101. The elongate body 112 issurrounded by a protective structure (or “bumper”) 113 having an outercircumference of essentially circular cross section in a planeperpendicular to the longitudinal axis z of the antenna 101. The outercircumference of the protective structure 113 and the outercircumference of the elongate body 112 are essentially concentric. Whenthe antenna 101 is suspended by its own weight from the cable 102, thelatter also extends along the longitudinal axis z.

Keeping the antenna 101 in place in the aerial platform solely by meansof the cable 102 does not make it possible to obtain an adequate levelof safety when the aerial platform is in transit, in particular overpopulated areas. The cable 102 may break, it may be cut accidentally bythe pyrotechnic safety cutter, the brake on the winch 100 may fail andaccidentally release the cable. The loss of the antenna 101 represents aconsiderable financial loss but above all its large mass could fall intothe sea or to the ground causing serious material or human damage.

The position of the antenna 101 with respect to the winch 100 must belocked when it is in place on board the aerial platform. The detectiondevice therefore advantageously comprises a strapping device 104 servingto lock the position of the antenna 101 with respect to the winch 100 soas to prevent an accidental fall of the antenna and the associatedconsequences.

A prior art strapping device 104 is shown in FIG. 2 . It comprises astrap 105 comprising a clamping strip 106 and shoes 114 designed to beinterposed between the protective structure 113 and the clamping strip106. It also comprises a driving device 115 serving to move longitudinalends 110 and 111 of the clamping strip 106 with respect to one anotherso as to reduce the size of the loop in order to be able to grip anobject, for example the protective structure 113 of the antenna 101,during a so-called clamping step, or to increase the size of the loop inorder to be able to unclamp or release an object initially gripped bythe strap 105, during a so-called unclamping step.

Each end 110 and 111 of the clamping strip 106 is rigidly connected to anut 121 and 122, respectively, in terms of translation with respect tothe threaded rod 118 along the axis x. The nuts are engaged with screwthreads of the threaded rod which screw threads are produced withopposite hand so that clamping and unclamping are achieved by themovement of the ends of the clamping strip 106 in opposite directionsalong the longitudinal axis of a threaded rod 118. The rotationaldriving of the threaded rod 118 may be achieved by a motor, not shown,or by an operator by means of a knob, via gearing, not shown.

The clamping of the strip 106 needs to be limited in order to avoiddamaging the antenna or damaging the screw-nut system or, more simply,to allow unclamping. Specifically, excessive clamping may lead to thenut becoming jammed on the threaded rod, requiring the application ofexcessive torque in order to free the antenna. It is possible to limitthe travel both on clamping and on unclamping.

In order to limit the travel of the nuts, the driving device comprises acontrol member for controlling the motor, and two position sensors fordetecting the limit loop sizes in the clamping and unclampingdirections. The control member stops the motor after detection of limitloop sizes.

As may be seen in FIG. 2 , each position sensor comprises a push-buttonswitch 123 and 124 fixed to the frame 109, and an actuator, in the formof a stop 125 and 126, respectively, fixed to one of the nuts 121 and122 respectively. The stop 125 comes to bear against the push-button 127of the switch 123 and pushes it perpendicular to the axis x of thethreaded rod 118, so as to close the switch 123 when, during theunclamping phase, the size of the loop reaches a threshold value thatcorresponds to a threshold position of the nut 121 along the threadedrod 118 in unclamping. The stop 126 comes to bear against thepush-button 128 and pushes it perpendicular to the axis x of thethreaded rod 118, so as to close the switch 124 when, during theclamping phase, the size of the loop reaches another threshold valuethat corresponds to a threshold position of the nut 122 along thethreaded rod 118 in clamping. Ramps pivoting about axes perpendicular tothe plane of FIG. 2 are provided at the interface between eachpush-button 127 or 128 and its stop 125 or 126 so as to avoid damage tothe push-button 127 or 128.

Now, the Applicant Company has found that the sensors lose theircalibration during operation, with the consequence of altering thedetected threshold size values and leading to excessive clamping and/orunclamping that may damage the driving device and the antenna. In orderto avoid these excesses, the sensors need to be regulated prior to eachoperation.

SUMMARY OF THE INVENTION

It is one object of the invention to propose a driving device comprisinga position sensor able to detect a predetermined position more reliably.

To this end, one subject of the invention is a driving devicecomprising:

-   -   a frame,    -   a screw-nut system comprising a threaded rod and a first nut        helicoidally connected to the threaded rod, the threaded rod        being connected to the frame by a pivot connection that allows        the threaded rod to rotate with respect to the frame about a        longitudinal axis of the threaded rod,    -   a first position sensor making it possible to detect a limit        position of the first nut along the longitudinal axis, the first        position sensor comprising a first part and a second part, the        first position sensor being sensitive to a variation in a        distance between the first part and the second part of the first        position sensor along the axis,    -   the first part being fixed to the first nut and the second part        being connected to the threaded rod without passing via the        pivot connection and in such a way that rotation of the threaded        rod about the longitudinal axis leads to a variation in the        distance between the first part and the second part of the first        position sensor along the longitudinal axis.

Advantageously, the device comprises at least one of the below featuresconsidered alone or in combination:

-   -   the second part of the first sensor is helicoidally connected to        the threaded rod,    -   the screw-nut system comprises a second nut in helicoidal        connection with the threaded rod, the first nut being engaged        with a first screw thread of the threaded rod and the second nut        being engaged with a second screw thread of the threaded rod,        the first screw thread and the second screw thread being        produced with opposite hand, the driving device comprising a        second position sensor making it possible to detect a limit        position of the second nut along the longitudinal axis with        respect to the frame, the second position sensor comprising a        first part and a second part, the second position sensor being        sensitive to a variation in the distance between the first part        and the second part of the second position sensor along the        axis,        the first part of the second position sensor being fixed to the        second nut and the second part of the second position sensor        being connected to the threaded rod without passing via the        pivot connection and in such a way that rotation of the threaded        rod about the longitudinal axis leads to a variation in the        distance between the first part and the second part of the        second position sensor along the longitudinal axis,    -   the first screw thread and the second screw thread have the same        pitch referred to as the first pitch,    -   the second part of the second sensor is helicoidally connected        to the threaded rod,    -   the second part of the two sensors is engaged with the one same        additional screw thread,    -   the second screw thread has a second pitch, the additional screw        thread being produced with the same hand as the second screw        thread and having a third pitch different from the second pitch,    -   the additional screw thread is interposed between the first        screw thread and the second screw thread and has a third pitch        longer than the first pitch,    -   the first part and the second part of the first sensor comprise        a push-button switch and an actuator for actuating a push-button        of the push-button switch in order to bring about a change in        state of the switch,    -   the first position sensor is configured to be sensitive to a        variation in distance between its first part and its second part        along the axis x, but not to a variation in relative angular        position between its first part and its second part about the        axis x,    -   the push-button is in a sliding connection parallel to the        longitudinal axis with a fixed part of the switch and the stop        extends in a plane substantially perpendicular to the        longitudinal axis,    -   it comprises a motor coupled to the threaded rod in order to        allow the threaded rod to be rotationally driven about its        longitudinal axis,    -   it comprises a control member making it possible to control the        motor, the control member receiving measurements emanating from        the first position sensor and being able to control the motor on        the basis of the measurements,    -   the control member receives measurements emanating from the        second position sensor, the control device being configured to        stop the motor as soon as the limit position of the first nut is        detected when the threaded rod is rotating in a first direction,        and, after a delay, following detection of the limit position of        the second nut, when the threaded rod is rotating in the        opposite direction.

The invention also relates to a strapping device for binding an objectby means of a strap comprising a clamping strip comprising a first endand a second end and forming a loop that is intended to surround theobject, the strapping device comprising a driving device according tothe invention, allowing the two ends to move with respect to one anotherso as to enlarge or decrease the size of the loop, the first end of thestrap being rigidly connected to the first nut in terms of translationalong the axis of the threaded rod.

Advantageously, the second end is rigidly connected to the second nut interms of translation along the axis of the threaded rod.

The loop may be closed.

The invention also relates to a holding device for clamping a hollowobject, said device comprising a first pad and a second pad which arecapable of pressing against a hollow object, on the interior of thehollow object, the holding device comprising a driving device accordingto the invention, the driving device being configured to move the twopads in relation to one another so as to move them away from one anotherin order to clamp the object or to move them closer together in order torelease the object, the first pad being rigidly connected to the firstnut in terms of translation along the axis of the threaded rod, thescrew-nut system comprising a second nut engaged with a second screwthread which is formed with the opposite hand to the first thread, thesecond pad being rigidly connected to the second nut in terms oftranslation along the axis of the threaded rod.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on studying a few embodimentsdescribed by way of completely non-limiting example and illustrated byappended drawings, in which:

FIG. 1 , which has already been described, shows, schematically, adetection device,

FIG. 2 shows a schematic cross section of a strap encircling an antennaand of a driving device of the prior art,

FIG. 3 schematically shows a strapping device according to theinvention,

FIGS. 4 and 5 schematically show the driving device in greater detail incross section (FIG. 4 ) and in perspective (FIG. 5 ),

FIG. 6 is a simplified kinematic diagram of the driving device,

FIG. 7 shows a partial view of a holding device according to theinvention.

DETAILED DESCRIPTION

From one figure to another, the same elements are denoted using the samereference numbers.

The invention relates to a driving device with a screw-nut system. Thisdevice can be used in a strapping device 4 intended to be incorporatedinto an airborne warfare device or detection device as shown in FIG. 1 .The strapping device 4 therefore replaces the strapping device 104. Theinvention also relates to the strapping device 4 and the detectiondevice as shown in FIG. 1 , comprising the strapping device 4 accordingto the invention. The strapping device 4 may more generally be used togrip any type of object, preferably one with a circular cross section.

The driving device with a screw-nut type system may be used for devicesother than the strapping devices that require a nut to be driven along athreaded rod and detection of a position of the nut along the screw. Byway of example, the driving device can be implemented in a machine toolin which a plate is being translationally moved. Use of the invention isof benefit in detecting a position of the plate.

As visible in FIG. 3 , the strapping device 4 according to the inventioncomprises a strap 5 designed to bind an object, for example an antenna101 and, more specifically, its protective bumper 113, for example ofessentially circular cross section, and allowing the object to begripped or released. The strap 5 comprises a clamping strip 6 forming aloop intended to bind the object 101. The clamping strip 6 comprises twolongitudinal ends 10 and 11.

The strapping device 4 also comprises a clamping/unclamping device 15 ordriving device serving to move ends 10 and 11 of the clamping strip 6with respect to one another so as to reduce the size of the loop inorder to be able to clamp an object, for example the antenna 101, duringa so-called clamping step, or to increase the size of the loop in orderto be able to unclamp or release an object initially clamped by thestrap 5, during a so-called unclamping step. To vary the size of theloop is to vary the length of the perimeter of the loop, that is to saythe diameter of the loop. Shortening of the perimeter of the loop, whicharises during clamping, produces a pressure on the object 101 that is tobe clamped, and creates an assembly by clamping between the strap 5 andthe object 101. In order to maintain the clamping of the object 101, theclamping/unclamping mechanism 15 maintains tensile forces on the freeends of the strap 5. A frame 19 delimits a housing 19 a accommodatingthe strap 5. The housing 19 a here has a circular cross section in theaxis z (perpendicular to the plane of FIG. 3 ).

The clamping/unclamping device 15 comprises a screw-nut systemcomprising a threaded rod 18 and at least one nut 20. More precise viewsof the driving device 15 are shown in FIG. 4 (in cross section) and inFIG. 5 (in perspective).

The threaded rod 18 is connected to the frame 19 by a pivot connection218 visible in FIG. 3 , allowing the threaded rod 18 to rotate withrespect to the frame 19 about a longitudinal axis x of the threaded rod18. The connection 218 is formed for example by two plain bearingsproduced respectively in two plates 218 a, 218 b rigidly connected tothe frame 19, visible in FIG. 4 , and spaced apart along the axis x. Theconnection 218 may be achieved in a different way, for example by meansof one or two rolling bearings.

The screw-nut system also comprises a first nut 20 connected in ahelicoidal connection to the threaded rod 18 and to the frame 19 by aconnection that prevents the nut from rotating with respect to the frame19 about the axis x. In FIG. 5 , plates 220 a and 220 b, which areparallel to one another and to the axis of the rod 18, are positioned oneither side of the nut 20 so as to clamp the nut 20. The screw-nutsystem comprises a second nut 21 connected in a helicoidal connection tothe threaded rod 18 and connected to the frame 19 by a connection 221 a,221 b that prevents the nut 21 from rotating with respect to the frame19 about the axis x. In FIG. 5 , plates 221 a and 221 b, which areparallel to one another and to the axis of the rod 18, are positioned oneither side of the nut 21 so as to clamp the nut 21. The plates 220 a,220 b and 221 a and 221 b are pivotably connected (about an axisperpendicular to the axis x) to the ends 10 and 11, respectively, of theclamping strip 6 which ends are themselves prevented from rotating withrespect to the frame 19 about the axis x by the clamping strip 6 beingimmobilized in the housing 19 a.

The nut 20 is engaged with a first screw thread 22 of the threaded rod18, shown schematically in FIG. 3 , and the nut 21 is engaged with asecond screw thread 23 of the threaded rod 18. The screw threads 22 and23 are produced with opposite hand and may have the same pitch.Different pitches are equally possible. The first end 10 of the clampingstrip 6 is rigidly connected to the nut 20 in terms of translation withrespect to the frame 19 along the axis x, and the second end 11 of theclamping strip 6 is rigidly connected to the nut 21 in terms oftranslation with respect to the frame 19 along the axis x. As a result,the screw-nut system is configured to move the two ends of the clampingstrip 10 and 11 in opposite directions parallel to the axis x withrespect to the frame 19 when the threaded rod 18 is rotated about itsaxis in one direction (clamping) and in the opposite direction(unclamping). The ends 10 and 11 move closer together during unclampingand move further apart during clamping. In the embodiment in thefigures, each end 10 and 11 is in a pivot connection with a nut 20 and21 respectively, about an axis perpendicular to the plane of the loopformed by the clamping strip 6. As an alternative, the ends 10 and 11may be rigidly connected to the respective nuts 20 and 21, namely fixedto the nuts or of one-piece with the nuts.

In the embodiment of the figures, the screw-nut system comprises twonuts 20 and 21 each connected to a respective end 10 and 11. As analternative, it comprises a single nut helicoidally connected to thethreaded rod 18 and immobile in terms of rotation about the axis x withrespect to the frame 19 and rigidly connected to one of the ends of theclamping strip in terms of translation with respect to the frame alongthe axis x so as to be able to drive this end along the axis x withrespect to the frame. The other end is, for example, fixed to the frame19.

As can be seen in FIG. 5 , the clamping/unclamping device comprises agearset 30 comprising two gear wheels 33, 34 engaged with one anotherfor driving the rotation of the screw. A motor 50 (shown in FIG. 5 ) isable to drive the rotation of the wheel 34. The gearset 30 transmitsthis rotational movement to the threaded rod 18 via the wheel 33. Themotor 50 is, for example, coupled to the wheel 34 by means of reductiongearing, not shown.

The driving device 15 comprises a control member 61 for controlling amotor 50. This member controls the motor on the basis of informationemanating from the position sensors 70, 80 shown in FIG. 3 . Eachposition sensor 70 or 80 is able to detect a predetermined position of anut 20 or 21 with respect to the threaded rod 18 along the longitudinalaxis x corresponding to a given size of the loop. The sensor 70 isconfigured to detect a limit position of the nut 20 relative to thethreaded rod 18 along the axis x corresponding to a limit unclampingloop size. The sensor 80 is configured to detect a limit position of thenut 21 relative to the threaded rod 18 along the axis x corresponding toa limit clamping loop size. The limit positions of the two nuts alongthe axis x are different.

The control member 61 is configured to stop the motor 50 when the limitunclamping size is reached while the threaded rod 18 is rotating in adirection corresponding to unclamping and when the limit clamping sizeis reached while the threaded rod 18 is rotating in the oppositedirection. These stoppages may be instantaneous or delayed as we shallsee later.

As visible in FIG. 3 , each sensor 70 or 80 comprises two parts of whicha first part 71 or 81 is fixed to the corresponding nut 20 or 21respectively. In other words, each first part 71 and 81 is helicoidallyconnected to the threaded rod 18 via one of the nuts 20 and 21respectively.

Each sensor comprises a second part 72 which in this instance is commonto the two sensors 70 and 80 and forms a plate perpendicular to the axisx which plate will be described more specifically later on. The secondpart 72 is mounted in such a way that the rotation of the threaded rod18 about a longitudinal axis x of the threaded rod 18 leads to avariation in distance between the first part 71 or 81 and the secondpart 72 of the position sensor 70 or 80 respectively, along thelongitudinal axis x of the threaded rod 18, the position sensor 70 or 80respectively being configured in such a way as to be sensitive to thisvariation in distance.

According to the invention, as visible in FIG. 3 , the second part 72 isconnected to the threaded rod 18 without passing via the pivotconnection 218 shown in FIG. 3 . Specifically, the pivot connection 218has axial play along the axis x. This is an imperfect pivot connection.With the setup according to the invention, the play in this highlystressed connection 218 has no impact on the regulation of the sensorwhich therefore has the advantage of being stable, accurate and undercontrol. The play in the pivot connection 218 between the two parts ofeach sensor 70, 80 is saved.

In the embodiment shown in the figures, the part 72 is helicoidallyconnected to the threaded rod 18 and is connected to the frame 19 by aconnection that prevents the part 72 from rotating with respect to theframe 19. This is achieved by means of two prongs 272 a, 272 b visiblein FIG. 5 , extending longitudinally along the axis x, and spaced apartalong an axis perpendicular to the axis x in such a way as to clamp ablock 200 rigidly connected to the plates 220 a and 220 b which arethemselves prevented from rotating with respect to the frame 19 aboutthe axis x.

The part 72 is therefore engaged with a screw thread 73, indicatedschematically in FIG. 3 , of the threaded rod via a nut 24.

As an alternative, one part of the two parts of a position sensor can beconnected to the threaded rod 18 by rendering it immovably attached tothe threaded rod 18, or alternatively by fixing it to the threaded rod18 in terms of translation along the axis x and by fixing it to theframe 19 in terms of rotation about the axis x. These connections do notpass via the pivot connection 218.

In the nonlimiting embodiment of the figures, as visible in FIG. 4 , thefirst part 71, 81 of each sensor is a push-button switch. The secondpart 72 is an actuator produced, in this instance, in the form of astop. The actuator 72 allows the push-button 75 or 85 to be actuated inorder to bring about a change in state of the switch. Each switch isable to be either in a closed state, or in an open state. A change instate of the switch corresponds to a transition from the open state tothe closed state, or vice versa.

The first switch 71 and its actuator 72 are configured and arranged insuch a way that the first actuator 72 brings about a change in state ofthe first switch 71 when the first nut 20 reaches its limit positionwith respect to the threaded rod 18 along the axis x. This limitposition corresponds to the limit unclamping size of the loop. Thesecond switch 81 and the second actuator 72 are configured and arrangedin such a way that the second actuator 72 brings about a change in stateof the second switch 81 when the second nut 21 reaches its limitposition with respect to the threaded rod 18 along the axis x. Thisposition corresponds to the limit clamping size of the loop. Thechange-of-state information for each switch is transmitted to thecontrol member 61.

The push-button switch 71 or 81 is fixed to a nut 20 or 21. Thepush-button switch 71 or 81 comprises a fixed part 74 or 84 rigidlyconnected to the nut 20 or 21. The fixed part 74, 84 comprises acircuit, not shown. The switch comprises a push-button 75 or 85, able tomove translationally with respect to the fixed part 74 or 84. The fixedpart 74 or 84 comprises a contact of the normally-open type. Thepush-button 75 or 85 may come into physical contact with a circuit ofthe fixed part in order to close the circuit. The switch thentransitions into the closed state. The switch is open when thepush-button is distant from the circuit. As an alternative, at least oneswitch has a contact of the normally-closed type.

The push-buttons 75 and 85 are capable of translational movement withrespect to the respective fixed parts 74 and 84 substantially parallelto the axis x. In other words, each push-button 75 or 85 is in a slidingconnection with its nut 20 or 21 parallel to the axis x. Eachpush-button 75 or 85 is interposed between the contact of its switch 71or 81 and the stop 72 along the axis x. the push-button 75 or 85 willtherefore close the switch 71, 81 when the stop 72 comes closer to thefixed part 74 or 84 and will push the push-button 75 or 85 until itmakes contact.

As visible in FIG. 3 , the stop 72 is engaged with a screw thread 73 ofthe threaded rod which screw thread is of the same hand as the screwthread 23 (engaged with the nut 21) but of opposite hand to the screwthread 22 (engaged with the nut 20). The screw thread 73 has a differentpitch from the screw thread 23 so as to be able to cause the two parts72 and 71 to move closer together at least when the threaded rod isrotating in one direction. In the nonlimiting example of the figures,the screw threads 22 and 23 have a pitch of 1.5 mm/turn, the screwthread 73 has a pitch of 1.75 mm.

The operation of the device is as follows. Starting from an initialposition in which the central nut 24 (or the stop 72) is in a centralposition, the clamping strip 6 is in an intermediate position somewherebetween clamped and unclamped. By maneuvering the threaded rod 18 in onedirection about the axis x, the stops 20 and 21 move in oppositedirections because the screw threads 22 and 23 are produced withopposite hand. If, for example, this is the unclamping direction, thenuts 20 and 21 move closer together, carrying with them the ends 10 and11 of the clamping strip 6. The size of the loop increases. The stop 72moves in the opposite direction to the nut 20 and closer thereto. Thestop 72 moves toward the push-button 75 at a rate of 3.75 mm/turn. Thestop 72 comes into contact with the first push-button 75, moves it, withrespect to the fixed part 74, in the direction x and in the sense ofdirection of movement of the stop 72 and thus brings it into contactwith the contact of the switch 71 so as to bring about the change instate of the switch 71. The limit position of the nut 20, along the axisx, relative to the threaded rod 18, corresponding to the limitunclamping size of the loop is therefore detected. This information issent to the control member 61. Advantageously although not necessarily,the control member 61 is configured to stop the motor 50 as soon as thelimit position of the nut 20 is detected when the threaded rod 18 isrotating in the unclamping direction. The strap 6 is, for example, fullyretracted into its housing 19 a in the frame 19 and must not beretracted any further into it in case it should become jammed therein.Stoppage therefore has to be highly accurate because, for the nextrecovery of the antenna, it is necessary to be certain that thestrapping is open to the maximum but without the risk of jamming. Thishigh relative speed between stop 72 and the first push-button 75 allowsfor highly precise adjustment. On opening, a well-regulated strap 6 willalways be in the same position when it stops moving. As an alternative,the control member 61 stops the motor 50 with a delay after detectingthe limit position of the nut 20 during unclamping, namely when thethreaded rod 18 is rotating in the direction of clamping.

Now, when the motor 50 causes the threaded rod 18 to rotate in theopposite direction about the axis x, namely in the direction ofclamping. The nuts 20 and 21 moving in opposite directions move awayfrom one another and the size of the loop decreases. The stop 72 movesin the same direction as the nut 21 but a little faster because itspitch is 1.75. The stop 72 will therefore catch up with the push-button85 little by little at a rate of 0.25 mm/turn. The stop 72 ultimatelycatches up with the push-button 85, moves it translationally along theaxis x toward the contact of the fixed part 84, thereby bringing aboutthe change in state of the switch 81. The limit position of the nut 21,relative to the threaded rod 18, along the axis x corresponding to thelimit clamping size of the loop is detected. This information istransmitted to the control member 61 which stops the motor in order tostop the clamping, preferably, although not necessarily, with a delayfollowing receipt of the detection information. When the limit clampingsize is reached, the motor continues to drive the rod 18 in order totighten the clamping strip until the loop reaches a predeterminedthreshold size. This guarantees that the antenna is completely clampedwhatever the diameter of the antenna within a predetermined range ofdiameters. It may be seen that the clamping still enjoys a broad rangeof uncertainty since the rate of advance of the contact is only 0.25mm/turn in relative terms. This broad range means that antennas ofdifferent diameters can easily be accommodated provided that the delayto actual stoppage of the motor after contact is sufficient.Furthermore, the low relative rate of advance between the two parts ofthe switch 81 makes it possible not to damage the push-button 85 whenthe motor is stopped with a delay following detection of the limitclamping position. The push-button 85 continues to be depressed, but ata low speed. The maximum travel of the push-button 85 can therefore bereduced, so the switch is therefore compact. As an alternative, thecontrol member 61 is configured to stop the motor 50 as soon as theinformation regarding the change in state of the switch 81 is receivedwhen the threaded rod is rotating in the clamping direction.

In the non-limiting embodiment of the figures, the sensors 70 and 80comprise the one same actuator 72 which in this instance is a lateextending essentially in a plane perpendicular to the axis x. This stop72, which is common to the two sensors, is engaged with a screw thread73 positioned between the other two screw threads 22 and 23. Thisembodiment is particularly advantageous because it is compact andrequires few components.

Advantageously, the pitch of the third screw thread 73 engaged with thestop 72 is longer than the pitch of the second screw thread 23. Thatmakes it possible to ensure that the nut 21 and the stop 72 move closertogether when the rod rotates in the clamping direction and furtherapart when the rod 18 rotates in the opposite direction.

Advantageously, as is the case in the embodiment in the figures, thepitch of third screw thread 73 is longer than that of the first screwthread 22. The rate at which the nut 20 and stop 72 move towards oneanother when moving in opposite directions is therefore high and allowsthe movement to stop at precise position.

As an alternative, the second parts of the two sensors are distinct. Itis possible for example to provide one stop per sensor. These secondparts may then be engaged with different screw threads of the threadedrod. At least one of the sensors may have a second part that is fixedwith respect to the threaded rod or at least fixed in terms oftranslation with respect to the threaded rod. At least one of the secondparts is engaged with a screw thread positioned outside the spacedelimited by the screw threads 22 and 23 along the axis x.

The first part and the second part of at least one sensor may beswitched over. For example, the first part of at least one sensor is anactuator and the second part of at least one sensor is a push-button. Itis possible, for example, to fix at least one of the two push-buttonswitches to fix the nut 24 and to fix the corresponding actuator to thenut 20 or 21. It is possible for example to fix the two switches to thenut 21 by arranging them in opposite directions along the axis x and toprovide two fixed stops for the nuts 20 and 21 respectively.

In the embodiment of the figures, the sensors 70, 80 are of theactuator/push-button switch type. As an alternative, at least one sensoris another type of sensor. This may, for example, be a magnetic sensor,an optical sensor, an inductive-type sensor, a Doppler-effect sensorable to detect a variation in distance between two parts of the sensoralong the axis x. However, these sensors require processing in order todetect the desired position. These sensors may also have a second partthat is common, or distinct second parts. One sensor may suffice,depending on circumstances.

Advantageously, each sensor, or at least one sensor, is configured andarranged to be sensitive to a variation in distance between its twoparts parallel to the axis x but not to a variation in relative angularposition between its two parts about the axis x. That makes theregulation of the sensor insensitive to the angular play in theconnection of its nut with respect to the frame. Moreover, since onlythe axial relative movement is taken into consideration, if the parts ofa sensor should move tangentially or radially relative to the rod alongthe axis x (because of the play in the helicoidal connection), this isof absolutely no importance because their relative distance along theaxis x does not vary. The solution is therefore highly insensitive toexpansions, vibrations, movements, and as long as the regulated distancebetween the two parts of the position sensors does not vary, the strapwill open and tighten in the same way.

This is, for example, the case in the embodiment in the figures, inwhich each sensor 70 and 80 comprises a stop 72 extending substantiallyin a plane perpendicular to the axis x and a push-button switch 71 or 81comprising a push-button 75 or 85 in sliding connection with a nut 20 or21 respectively, parallel to the axis x. This solution offers theadvantage of being compact and simple. It may be achieved usingpush-buttons of reasonable diameter compatible with the aeronauticalfield. Moreover, this embodiment does not, as does the prior art,require the installation of a pivoting ramp in order for the drivingdevice to be able, without damage, to tolerate the fixed part of theswitch and the stop moving closer together after the closing of theswitch. The very nature of the push-button allows this movement. It istherefore possible to dispense with a painstaking step of setting up theramp and the relative position of the ramp and of the stop along theaxis y. This is also for example the case with an optical sensorcomprising a source emitting a ray of light parallel to the axis x, asecond part in the form of a reflective plate perpendicular to the axisx and a detector capable of detecting a ray reflected by the panel andmeasuring the difference in a physical parameter between the incidentray and the reflected ray and from this deducing a distance between theplate and the source along the axis x.

As an alternative, the sensor is sensitive to the variation in relativeangular position between its two parts about the stop. For example, theposition sensors have an arrangement similar to that of the prior art.

The driving device 15 also comprises a knob 52, visible in FIG. 5 ,secured in rotation to the wheel 33 about its axis of rotation. Thisknob allows an operator to turn the rod by hand.

FIG. 6 is a simplified kinematic diagram of the driving device. Thehelicoidal connections 220 and 221 between the respective nuts 20 and 21and the threaded rod are shown, as are the pivot connections 218 and 340between the frame 19 and the threaded rod 18 and, respectively, thewheel 34. It will be noted also that the push-buttons 75 and 85 are insliding connection with the fixed parts 74 and 84 of the respectiveswitches. The connections that prevent the nuts from rotating withrespect to the frame are not shown.

Advantageously, as shown in FIG. 6 , the driving device 15 comprises atorque limiter 54 configured and arranged in such a way as to eliminatethe transmission of torque between the motor 50 and the threaded rod 18when the torque about the axis of the threaded rod exceeds apredetermined threshold. Advantageously, to complement the torquelimiter 54, the movement transmission device comprises a freewheel 55.The torque limiter 54 and the freewheel 55 are configured and arrangedin such a way as to make it possible to limit a torque rotating thethreaded rod 18 about the axis x in one direction of rotation only inwhich the freewheel 55 allows rotation and therefore slippage in thetorque limiter. In the other direction, the freewheel does not permitany rotation and the torque limiter is unable to act. Advantageously,the direction of rotation in which the torque limiter acts is thedirection corresponding to clamping. This device makes it possible toprevent the clamping torque from exceeding a predetermined thresholdwhich is the same regardless of the diameter of the antenna. Delayedstoppage of the motor during clamping makes it possible to guaranteethat the torque limiter slips before the motor stops. By contrast, thetorque limiter does not come into action in the unclamping direction.Limiting the angular travel of the threaded rod in the clampingdirection makes it possible to ensure that an operator or that the motor50 will be able to re-tighten the clamping strip after unclamping, thetorque limiter acting only during clamping.

The motor 50 is coupled to the second wheel 34 by means of the torquelimiter 54 and by means of the freewheel 55, if present. The freewheel55 allows the coupling/uncoupling of two shafts 56 and 57 connected tothe frame 19 by pivot connections 340 and 341, respectively. A firstshaft 56 is rigidly connected to the wheel 34 and the other 57 is ashaft of the motor 50.

In the embodiment in the figures, the clamping strip 6 forms a closedloop. In other words, the clamping strip comprises two strip strands 7and 8 referenced in FIG. 4 , each comprising one of the two ends 10 and11 of the clamping strip 6 and crossing one another in such a way that aclosed loop intended to completely end circle the object that is to beclamped, namely to make a complete turn around the object, is formed bythe clamping strip 6. The use of a strip 6 forming a closed loop by thecrossover of two strip strands makes it possible to significantly varythe size of the loop and thus to grip and release objects havingdifferent diameters. As an alternative, the clamping strip 6 does notform a closed loop. In that case, its ends move closer together duringclamping and further apart during unclamping. In that case, the two endsmove closer together during clamping and further apart duringunclamping. It is then conceivable to provide second parts, for examplestops, that are distinct for the two sensors, engaging with differentscrew threads positioned on the outside of the space delimited by thetwo screw threads 22 and 23.

The clamping strip 6 comprises for example a metal ribbon or a strip ofplastic material. The perimeter or size of the loop varies, for example,during clamping, by varying the bending of the clamping strip. The stripadvantageously has a shape at rest that is such that the central partessentially follows the shape of the perimeter of the object that is tobe gripped.

The strap 5 also comprises shoes 14, distributed along the clampingstrip in such a way as to be intended to be interposed between theclamping strip 6 and the object 101 that is to be gripped. One shoe, notdepicted here, may bear against the two strip strands 7 and 8 so as tobe interposed between the two strip strands 7 and 8 and the object thatis to be gripped.

The control member 61 may comprise one or more dedicated electroniccircuits or a general-purpose circuit. Each electronic circuit maycomprise a reprogrammable computing machine (a processor or amicrocontroller for example) and/or a computer executing a programcomprising a sequence of instructions and/or a dedicated computingmachine (for example a set of logic gates such as an FPGA, a DSP or anASIC, or any other hardware module).

The driving device according to the invention may be incorporated intoanother type of holding device 350 as shown in FIG. 7 of the typecomprising two pads 310 and 320 intended to hold or release an object.For greater clarity, only the threaded rod (without the third screwthread), the nuts, the pads and the bars 312, 313 have been depicted,but the driving device is a driving device according to the invention.The pads 310 and 320 are respectively fixed in terms of translationalong the axis x to the nut 20 and to the nut 21 via bars 312 and 313respectively, which intersect. When the rod 18 is rotating in onedirection, the nuts 20 and 21 move closer together and the pads 310, 320move further apart so as to come to bear against a hollow body 314, forexample of cylindrical cross section, on the inside of the hollow bodyso as to apply forces in opposite directions parallel to the axis x, forexample opposing forces, to the hollow body in order to clamp the body.These forces are advantageously radial, along one and the same radialaxis defined for a circular cross section of a hollow body. When thethreaded rod 18 rotates in the opposite direction, the nuts move apartand the pads move closer together so as to move away from the hollowbody and release same. As an alternative, the direction in which thepads move is that of the nuts. For example, the bars 312 and 313 do notintersect. For greater clarity, only the two screw threads 22 and 23 ofthe threaded rod are depicted in FIG. 7 . The other elements of thedriving device are not shown; for greater clarity, the sensors and thethird screw thread are not shown in FIG. 6 . Advantageously, the torquelimiter 54 and the freewheel 55, if present, are arranged in such a wayas to make it possible to limit a torque rotating the threaded rod 18about the axis x in one direction of rotation, and possibly in thisdirection only. This direction of rotation is the directioncorresponding to clamping, namely the direction of rotation that causesthe two pads to move further apart and therefore causes the two nuts tomove closer together.

The invention claimed is:
 1. A driving device comprising: a frame; and ascrew-nut system comprising: a threaded rod connected to the frame by apivot connection that allows the threaded rod to rotate with respect tothe frame about a longitudinal axis of the threaded rod, the threadedrod comprises a first thread and an additional thread having a pitchthat is different from a pitch of the first thread; a first nuthelicoidally connected to the first thread of the threaded rod; and anadditional nut helicoidally connected to the additional thread; a firstposition sensor configured to detect a limit position of the first nutalong the longitudinal axis, the first position sensor comprising afirst part and a second part, the first position sensor being sensitiveto a variation in a distance between the first part and the second partof the first position sensor along the longitudinal axis, wherein thefirst part of the first position sensor comprises a first push-buttonswitch being fixed to the first nut and the second part being fixed tothe additional nut and thereby being connected to the threaded rodwithout passing via the pivot connection and in such a way that rotationof the threaded rod about the longitudinal axis leads to the variationin the distance between the first part and the second part of the firstposition sensor along the longitudinal axis; and wherein the second partof the first position sensor comprises an actuator for actuating apush-button of the first push-button switch in order to bring about achange in state of the first push-button switch, the actuator forming astop configured to move closer to the push-button of the firstpush-button switch when the threaded rod is rotated in a firstdirection, such that the stop is operable to change a state of the firstpush-button switch when the stop contacts the push-button of the firstpush-button switch.
 2. The driving device as claimed in claim 1, whereinthe second part of the first position sensor is helicoidally connectedto the threaded rod.
 3. The driving device as claimed in claim 1,wherein the screw-nut system comprises a second nut in helicoidalconnection with the threaded rod, the first nut being engaged with afirst screw thread of the threaded rod and the second nut being engagedwith a second screw thread of the threaded rod, the first screw threadand the second screw thread being produced with opposite hand, whereinthe driving device comprises a second position sensor configured todetect a limit position of the second nut along the longitudinal axiswith respect to the frame, the second position sensor comprising a firstpart and a second part, the second position sensor being sensitive to avariation in a distance between the first part and the second part ofthe second position sensor along the longitudinal axis, wherein thefirst part of the second position sensor comprises a second push-buttonswitch being fixed to the second nut and the second part of the secondposition sensor being connected to the threaded rod without passing viathe pivot connection and in such a way that rotation of the threaded rodabout the longitudinal axis leads to the variation in the distancebetween the first part and the second part of the second position sensoralong the longitudinal axis, and wherein the second part of the firstsensor is integrated with the second part of the second sensor.
 4. Thedriving device as claimed in claim 3, wherein the first screw thread andthe second screw thread have the same pitch referred to as the firstpitch.
 5. The driving device as claimed in claim 3, wherein the secondpart of the second position sensor is helicoidally connected to thethreaded rod.
 6. The driving device as claimed in claim 5, wherein thesecond part of the first position sensor is helicoidally connected tothe threaded rod, and wherein the second part of the first positionsensor and the second part of the second position sensor are engagedwith the additional thread.
 7. The driving device as claimed in claim 6,wherein the second screw thread has a second pitch, the additionalthread being produced with the same hand as the second screw thread andhaving a third pitch different from the second pitch.
 8. The drivingdevice as claimed in claim 4, wherein the additional thread isinterposed between the first screw thread and the second screw threadand has a third pitch longer than the first pitch.
 9. The driving deviceas claimed in claim 1, wherein the second part of the first positionsensor comprises an actuator for actuating a push-button of the firstpush-button switch in order to bring about a change in state of thefirst push-button switch.
 10. The driving device as claimed in claim 1,wherein the first position sensor is configured to be sensitive to avariation in distance between its first part and its second part alongthe longitudinal axis, but not to a variation in relative angularposition between its first part and its second part about thelongitudinal axis.
 11. The driving device as claimed in claim 10,wherein the second part of the first position sensor comprises anactuator for actuating a push-button of the first push-button switch inorder to bring about a change in state of the first push-button switch,and wherein the push-button is in a sliding connection parallel to thelongitudinal axis with a fixed part of the switch and a stop extends ina plane substantially perpendicular to the longitudinal axis.
 12. Thedriving device as claimed in claim 1, further comprising a motor that iscoupled to the threaded rod to allow the driving of the threaded rod sothat it rotates about its longitudinal axis.
 13. The driving device asclaimed in claim 12, further comprising a control member making itpossible to control the motor, the control member receiving measurementsemanating from the first position sensor and being able to control themotor on the basis of the measurements.
 14. The driving device asclaimed in claim 13, wherein the first screw thread and the second screwthread have the same pitch referred to as the first pitch, wherein thesecond part of the second position sensor is helicoidally connected tothe threaded rod, wherein the second part of the first position sensoris helicoidally connected to the threaded rod, and wherein the secondpart of the first position sensor and the second part of the secondposition sensor are engaged with the additional thread, wherein thesecond screw thread has a second pitch, the additional thread beingproduced with the same hand as the second screw thread and having athird pitch different from the second pitch, wherein the additionalthread is interposed between the first screw thread and the second screwthread and has a third pitch longer than the first pitch, wherein theadditional thread is interposed between the first screw thread and thesecond screw thread and has a third pitch longer than the first pitch,and wherein the control member receives measurements emanating from thesecond position sensor, the control device being configured to stop themotor as soon as the limit position of the first nut is detected whenthe threaded rod is rotating in a first direction, and, after a delay,following detection of the limit position of the second nut, when thethreaded rod is rotating in the opposite direction.
 15. A strappingdevice for binding an object by means of a strap comprising a clampingstrip comprising a first end and a second end and forming a loop that isintended to surround the object, the strapping device comprising adriving device as claimed in claim 1, allowing the two ends to move withrespect to one another so as to enlarge or decrease the size of theloop, the first end of the strap being rigidly connected to the firstnut in terms of translation along the longitudinal axis.
 16. A strappingdevice for binding an object by means of a strap comprising a clampingstrip comprising a first end and a second end and forming a loop that isintended to surround the object, the strapping device comprising adriving device as claimed in claim 3, allowing the two ends to move withrespect to one another so as to enlarge or decrease the size of theloop, the first end of the strap being rigidly connected to the firstnut in terms of translation along the longitudinal axis and wherein thesecond end is rigidly connected to the second nut in terms oftranslation along the longitudinal axis.
 17. The strapping device asclaimed in claim 15, wherein the loop is closed.
 18. A holding devicefor clamping a hollow object, said device comprising a first pad and asecond pad which are capable of pressing against a hollow object, on theinterior of the hollow object, the holding device comprising a drivingdevice as claimed in claim 1, the driving device being configured tomove the two pads in relation to one another so as to move them awayfrom one another in order to clamp the object or to move them closertogether in order to release the object, the first pad being rigidlyconnected to the first nut in terms of translation along thelongitudinal axis, the screw-nut system comprising a second nut engagedwith a second screw thread which is formed with opposite hand to thefirst screw thread, the second pad being rigidly connected to the secondnut in terms of translation along the longitudinal axis.
 19. The drivingdevice as claimed in claim 1, wherein the second part of the firstsensor forms a plate extending from the additional nut in a directionsubstantially perpendicular to the longitudinal axis of the threadedrod.